It is often necessary in medical procedures to be able to transport materials between body passageways and external areas in a secure and accurate manner. Typically, a catheter is inserted into a body passageway and a solution is either infused into the body from an external source, or fluid is drained out of the body to an external location.
Many types of balloon catheters are available for these procedures. For drainage of fluid from a body passageway, a single lumen catheter may be sufficient. For infusion, catheters may be provided with additional lumens for such functions as temperature or pressure sensing, or for infusing more than one fluid at the same time without mixing prior to infusion. In some cases, a single catheter having multiple lumens is useful for simultaneous drainage and infusion.
In many of these procedures, proper placement of the catheter within the body passageway is important to the safety of the patient and success of the procedure. In some cases, a precise placement of the catheter is necessary throughout the procedure. Yet, movement in the region where the catheter is located sometimes causes the catheter to be dislodged from its original position within the passageway. As a result, the smooth flow of fluid into or out of the body can be disrupted or can be directed to or from an improper location. In addition, movement of a catheter within a body passageway may also cause damage to surrounding tissues.
It will be appreciated that a seal must be formed between the catheter and the body passageway for the procedures to be completely successful. For example, when infusing fluids, such infusion is performed under pressure to obtain a desired result. Failure to effect a seal at the location of the balloon results in leakage, and concomitant failure to maintain the desired pressure within the body passageway.
The development of balloon catheters has increased the security of catheter placement within body passageways. These catheters employ a balloon, located at the distal end of the catheter, that, when inflated, wedges the catheter in place as the balloon engages the walls of the body passageway. The inflated balloon may also form the necessary seal between the inflated balloon and the body passageway.
Many different types of balloon catheters are in use today. For example, the balloon may be a manually inflatable balloon, wherein a special lumen in communication therewith is usually provided for inflation and deflation of the balloon. Air or fluid is passed through the special lumen into the balloon to cause inflation of the balloon, and is drained out of the balloon to cause deflation. When inflated, the balloon assists in retaining the catheter in place. When the user wishes to remove the catheter, he or she simply removes the air or fluid from the balloon until the balloon is deflated. The catheter may then be easily removed.
One example of a manually inflatable balloon catheter in use today is disclosed in U.S. Pat. No. 4,689,041 issued to Corday. Corday discloses a balloon catheter having a hollow secondary tube in fluid communication with the interior of the balloon. The secondary tube allows for inflation and deflation of the balloon.
Another manually inflatable balloon catheter is disclosed by U.S. Pat. No. 4,648,384 issued to Schmukler. In Schmukler, a pump is used to pump gas through an extra lumen into the balloon in order to inflate the balloon. For deflation, the gas is released.
A second type of balloon catheter employs a self-inflating balloon. This balloon is typically in direct communication with the main lumen through apertures on the lumen which open into the balloon. A solution flowing through the lumen would enter the balloon and cause inflation. Stopping the flow of the fluid would cause the balloon to drain and inflate.
One example of this type of catheter is disclosed in a European Patent No. 249,338 issued to Spector et al., wherein the balloon is inflated and deflated by flow of arterial blood through the main lumen. Another example is disclosed by U.S. Pat. No. 5,021,045 issued to Buckberg et al.
In the past, people have attempted to secure balloon catheters in place by raising the pressure within the balloon so that the balloon expands more tightly against surrounding tissues. Unfortunately, high pressures can cause damage to the tissues as the tissues themselves are stretched due to the pressure of the expanding balloon. In cases where the tissue being treated is already damaged or diseased, high pressures can aggravate the damaged tissues.
Cardiac surgery is one area where rapid, safe, and secure infusion of solution into the body is necessary. Since the early days of cardiac surgery, it has been recognized that in order to provide the optimum surgical conditions when operating on the heart, it is necessary to interrupt the normal operation of the heart. For obvious reasons, an arrested, flaccid heart is preferred during a cardiac surgical procedure over a beating heart with blood flowing through it. Thus, in order to be able to efficiently perform cardiac surgery, it is often necessary to use cardiopulmonary-bypass techniques and to isolate the heart from its life-giving blood supply.
The normal heart receives its blood supply through the left and right coronary arteries which branch directly from the aorta. Generally, the veins draining the heart flow into the coronary sinus which empties directly into the right atrium. A few veins, known as thesbian veins, open directly into the atria or ventricles of the heart.
The most recent method developed utilizes continuous warm blood cardioplegia. Warm oxygenated blood cardioplegia has certain theoretical advantages over cold cardioplegia, such as continuously supplying oxygen and substrates to the arrested heart while avoiding the side effects of hypothermia. Salerno, Thomas A. et al., "Retrograde Continuous Warm Blood Cardioplegia: A New Concept in Myocardial Protection" 51 Annual of Thoracic Surgery 245 (1991).
The use of warm blood cardioplegia to protect the myocardium has proven the most advantageous method of those used to date. Cardioplegia, which literally means "heart stop," may be administered in an antegrade manner (through arteries in the normal direction of blood flow), in a retrograde manner (through veins opposite the normal blood flow direction), or in a combination of retrograde and antegrade administration. Cardioplegic solutions, typically containing potassium, magnesium procaine, or a hypocalcemic solution, stop the heart by depolarizing cell membranes.
Warm-blood cardioplegia is often initiated by placing an aortic antegrade cardioplegia cannula followed by the placement of a retrograde coronary sinus catheter. A high-potassium (20-30 mEq KCl liter) warm blood cardioplegic solution is infused through the antegrade cannula to rapidly induce arrest. Following diastolic arrest, perfusion is switched to a low-potassium (8-10 mEq KCl liter) solution infused continuously through the retrograde coronary sinus catheter at an infusion pressure at the cannula tip of less than 40 mm Hg.
While warm-blood cardioplegia has some advantages over prior methods, one problem encountered in the retrograde administration of warm-blood cardioplegia occurs in the placement of the retrograde coronary sinus catheter. A normothermic coronary sinus is more distensible and dilated than a corresponding hypothermic coronary sinus. As a result, placement of the retrograde catheter is difficult to maintain. Catheters designed for use in hypothermic conditions become flaccid and do not retain the shape necessary to maintain proper positioning of the catheter.
The development of retrograde coronary sinus catheters with self-inflating balloons has increased the security of catheter placement. These catheters employ a balloon, located at the distal end of the catheter, that inflates as cardioplegic solution is infused through the catheter. The inflation of the balloon in the coronary sinus wedges the retrograde catheter in place as the balloon engages the walls of the coronary sinus.
While engagement of the walls of the coronary sinus serves to secure the retrograde catheter in place during hypothermic cardioplegia (when the walls of the coronary sinus are relatively less distensible and dilated), the inflatable balloons designed for hypothermic cardioplegia do not necessarily function well in a normothermic environment.
The increased distensibility and size of a normothermic coronary sinus relative to a hypothermic coronary sinus prevents the inflatable balloon from securing an adequate purchase upon the walls of the coronary sinus. Pressure from the inflatable balloon against the walls of the coronary sinus merely dilates the warm coronary sinus farther, resulting in slippage and displacement of the retrograde catheter within the coronary sinus.
Clearly, this is a potentially dangerous situation, and in any event degrades the effectiveness of the procedure. Although slippage and displacement is carefully monitored, it has continued to be a problem and a serious concern.